Underreamer



Oct. 29, 1929. 1. w. DOODY 1,733,452

UNDER-REAMER Filed Dec. 13. 1926 imn T Patented Oct. 29, 1929 UNITEDSTATES ATENT OFFICE UNDERREAIL EB Application filed December 13, 1828.

This invention relates to underreamers of the type utilized with thestandard method of drilling artesian and oil wells to enlarge the boreand permit the lowering of the well casing.

This invention relates particularly to the incorporation of importantimprovements in underreamers of the bowl type. In a bowl type ofunderreamer. the reaming cutters are carried by an expanding mechanismwhich is mounted Within the tubular or bowl body.

Underreamers of this type are subjected during the reaming operation tosevere upward and lateral thrust strains which frequently result in thebreaking off of the cutter heads and the loss of the same in the well.The shear of these cutter heads because of these strains is particularlydue to the fact that when the cutters are expanded to the ream- 0 ingposition, the same are diverted outwardly and downwardly from thereaming body and the blow struck by the tool has a tendency to spread orsplit the cutters apart during some periods of operation of the tool.During other periods of operation of the tool, particularly when thehole is approximately the diameter of the cutters, there is a tendencyto crush the cutters together to shear the same oil' in this direction.

An important object of this invention is to provide means on the cutterheads at the bottom of the reamer body for taking up the upward andlateral thrusts imparted to the cutter heads during the reamingoperation. Another object of this invention is to provide an underreamerof the bowl type having reamingcutters mounted below the body so as todirectly impartall end thrust to the body and in which tubular bodythere is provided a spreader block which is set within the body forexpanding the cutters outwardly to the reaming position.

Another object of this invention is to provide an underreamer of thebowl or tubular body type having an expanding reamer cutter mechanismmounted within the body and means offset relative to the axis of thebody for holding the expanding means.

Another object of this invention is to provide an underreamer of thebowl type and Serial No. 154,465.

an expanding reamer cutter mechanism mounted within the body andcarrying cutter heads having formed on their upper surface arcuaterecesses adapted to fit the end of the body of the underreamer toprovide thrust bearings to take up the end and lateral thrusts impartedto the body.

Another object of this invention is to provide an underreamer of thebowl or tubular body type having an expandible cutter unit including aspring adapted to yieldably urge the cutters to the expanded or reamingposition and which expansion means are so constructed as to enable theassembling of the same to place upon the spring tension before the unitis assembled within the tubular body.

Other objects and advantages of this invention will be apparent from thefollowing detailed description.

A preferred embodiment thereof is illustrated in the accompanyingdrawings, in which drawings:

Figure 1 is a sectional side elevation of an underreamer embodying thisinvention illustrating the same as in position with the cutters held ina non-reaming position and as passing through a section of the casing.

Figure 2 is a tragmental sectional elevation of the underreamerillustrating the cutters in the expanded position.

Figure 3 is an end sectional view taken substantially on the line 33 ofFigure 1.

Figure 4 is an end elevation.

In the preferred embodimentof this invention illustrated in theaccompanying draw ings, 1 illustrates a well hole in which a casing 2 isbeing lowered. The well hole 1 has been drilled to a diametersubstantially as illustrated at 3 and in order to lower the well casing2, it is necessary to ream out the hole 1 to a diameter larger than theexterior diameter of the casing 2.

It is customary in the art to employ an un derreanoer tor reaming outthehole 1 to a diameter sutiicicnt to permit the casing 2 to be lowered inthe well and it is for this use that the tool which is really anexpandible drill derives the name underreamer.

The underreamer embodying this invention comprises a tubular body 4having formed at its upper end a tool joint 5 by means of which the sameis secured to a cable or the like so as to permit the same to bereciprocated in the hole. The body 4 has an axial chamber 6 formedtherein, in which an expandible cutter unit 7 is mounted. The expandiblecutter unit 7 supports within the tubular body 4 cutter heads 8 belowthe lower end 9 of the body 4.

The cutters 8 may be of any suitable or desirable construction as iswell understood in the art and are provided near their upper surface 10with arcuate recesses 11 which lit the lower end 9 of the body 4. Theannular flange provided around the arcuate recesses 11 provides on itsinner surface 12 a bearing surface which acts to prevent the collapsingof the cutters 8 together when the cutters are expanded to the reamingposition. The lower surface 13 of the arcuate recesses 11 provide endthrust bearings against which the end 9 of the body 4 is engaged duringthe reaming operation so that all of the end thrust imparted to thecutters 8 during the operation of the tool is imparted directly upwardto the reamer body 4 and these end thrust bearing surfaces are providedat a point close to the point of engagement of the cutters 8 with theground so that the leverage incident to the operation of the cutters toproduce lateral thrust in the cutter heads 8 is reduced to a minimum.Mounted within the chamber 14, formed at the lower end of the body andat substantially the lowest extent thereof, is an expanding block 15which provides expanding bearing surfaces 16 which are taperedcomplementary to the expanding bearing surfaces 19 formed on the innersurface of the cutters 8, so that when the cutters 8 are both upwardfrom the position illustrated in Figure 1 to the position illustrated inFigure 2, the bearing surfaces 19 ride along the bearing surfaces 16 andcause the cutter heads 8 to be expanded outwardly. The bearing surfaces16 are positioned entirely below the lower end 9 of the body 4 and thebearing surfaces 19 are so positioned that the cutters 8 are entirelyexpanded outwardly before the lower end 9 of the body passes into thearcuate recesses 11.

The expanding unit mounted in the tubular body 4 is preferably of thefollowing construction and comprises a T-shaped stem 20, the prongs 21of which are releasably fitted within recesses 22 formed in the shanks23 of thecutter 8. The T-shaped stem extends upwardly into the axialchamber 6 and a spring 24 is mounted thereon. A head 25 preferablycomprising a hexagonal nut is screw-threaded to the upper end of thestem 20 and a bearing sleeve 26 is mounted on the stem 20 between thehead 25 and T prongs 21. The bearing sleeve 26 is slidably mounted onthe stem 20 and is engaged by one end of the spring 24. The opposite endof the spring 24 engages the head 25. Formed on the T-shaped stem 20below the sliding sleeve 26 is a pair of outwardly extending lugs ortrunnions 27. In assembling the expandible unit, the prongs 21 of theT-shaped stem 20 are first inserted within the recesses 22 of thecutters 8 and the sleeve 26 is then mounted on the stem 20. The spring24 is then mounted on the spring 20 and the nut 25 is screw,- threadedat the upper end of the stem until the tension is imparted to the spring24, the trunnions 27 holding the slidable sleeve 26. The expandible unitis then inserted in the body and an expanding wedge is passed through apair of alined slots 28 formed in the body 4 engaging the lower edge ofthe slidable sleeve 26, forcing'the same upward. The wedge (not shown)is pushed through the slots 28 and displaced by a key 29. Formed at theedge of the slots 28, on the outer surface of the body 4 are recessesthrough which cotter pins 30 are inserted into the ends of the key 29 tohold the same in position.

In order to permit the expanding mechanism to expand the cutters quicklywhen the underreamer is in the well, there is provided in the body 4 aport 31 through which the liquid mud or water which is within the bodyof the reamer may be expelled as the cutters are expanded into the body.

Inorder to permit lowering of the underreamer into the well, the cutters8 are moved to the non-reaming position as illustrated in Figure 1,against the tension of the spring 24, and are tied in this position bymeans of a wire or bale 32 and the underreamer is lowered into the wellto the bottom thereof and is then lifted and dropped to break the bale32 to permit the cutters 8 to be expanded by the spring 24 to theposition shown in Figure 2.

The key 29 passes through the body 4 and under the slidable sleeve 26 inoff-center position, as illustrated in Figure 2, so as to permit thesame to pass the stem 20.

Any suitable or desirable means may be provided for holding theexpanding block 15 in position at the lower end of the body so that thesame may be removable to permit replacement when worn,-which meanspreferably comprises a bolt 33 which is passed through the lower end ofthe body and through a central bore formed in the block 15. The head ofthe bolt 33 and the nut thereof may be counter-sunk within the body, asillustrated in Figure 4.

Having fully described a preferred embodiment of my invention, it is tobe understood that I do not wish to be limited to the exact detailsherein set forth, which may obviously be varied without departing fromthe spirit of my invention as set forth in the appended claims.

I claim:

1. In an underreamer, the combination with a tubular body, a pair ofreamer cutters having shanks adapted to extend into an axial chamberformed in the body, a spreader block removably mounted intermediate the5 shanks in the chamber, cutter head formed on the shanks below thebody, the cutter heads having arcuate pockets formed in their upper endsadapted to closely fit the periphery of the body, and means foryieldingly holding the cutters in expanded position.

2. In an underreamer, the combination With a tubular body, a pair ofreamer cutters having shanks adapted to extend into an axial chamberformed in the body, a spreader block removably mounted intermediate theshanks in the chamber, cutter heads formed on the shanks below the body,the cutter heads having arcuate pockets formed in their upper endsadapted to fit the end of the body, means for yieldably holding thecutters in expanded position, and means adapted to be inserted throughthe bore formed in the body in 01fset position for holding the lattersaid means. 3. In an underreamer, the combination of a tubular body, apair of reamer cutters having shanks adapted to extend into an axialchamber formed in the body, a T-shaped stem mounted Within the body andreleasably secured to the cutters, means for releasably 0 securing theT-shapecl stem in the body, a spring mounted on the stem, a sleeveslidably mounted on the stem and engaging one end of the spring, a headremovably secured to the body and engaging the other end of the asspring, trunnions formed on the stem and acting as limit stops to holdthe slidably mounted sleeve, cutter heads having arcuate recesses formedtherein into Which the end of the tubular body is fitted when thecutters are expanded to provide end and lateral thrust bearings and aspreader block mounted in said chamber intermediate said cutters whenthe cutters are expanded to form with the cutters and body a straightline of metal in contact from: one cutter through to the next cutter.

Signed at Los Angeles, California, this 6 day of Dec, 1926.

JOHN W. DOODY.

